1. ) Field of the Invention
The present invention relates to a drive pin having a head asymmetrically mounted on its shank and, more particularly, to an asymmetric drive pin used in combination with a wall anchor.
2. ) Description of the Prior Art
Back clip assemblies are usually used for mounting shelves on walls and include a body with a wall anchor extending therefrom and a rod engaging hook formed in it. Several back clip models are available on the market and some of them comprise a wall anchor with laterally expandable fingers to increase the anchoring strength. These fingers are expanded against the back side of a wall when a drive pin is inserted through the wall anchor as shown in U.S. Pat. Nos. 4,264,047; 4,669,936; and 4,722,648.
Shelves for wall mounting typically comprise back and front rods extending the length of the shelf, parallel to each other, and regularly spaced parallel cross rods, perpendicular to the back and front rods. The cross rods have a rear and a front ends. The rear and frond ends are respectively mounted on the upper side of the back and front rods. The cross rods are sufficiently close to each other to support articles, even small ones, on them.
For mounting a shelf on a wall, at least two back clips are mounted on the wall, at the same height with respect to the ground. The back rod of the shelf is inserted in the rod engaging hooks of the back clips.
Two major problems occur with this type of fastening device. On one hand, the back rod is often released from the rod engaging hook due to a pressure applied on the shelf. On the other hand, the drive pin is sometimes released from the wall anchor due to a pressure applied on the expandable fingers. To overcome these problems, U.S. Pat. No. 4,669,936 discloses a back clip with a stop member, having a recess in it, and pivotally mounted on the upper part of the clip. Once the back rod of the shelf is inserted in the hook, the stop member is pivoted downwardly and the head of the drive pin is covered by the stop member, inside its recess portion. In this position, the stop member blocks the release of the shelf back rod from the hook and, at the same time, covers the head of the drive pin. However, interference frequently occurs between the stop member and the cross rods since the back clips are often installed without prior consideration for the cross rod location, and the stop member is significantly wide. When interference occurs, the stop member then cannot be pivoted downwardly. U.S. Pat. No. 4,722,648 solved a part of this problem by providing recesses and notches on opposite sides of the stop member. These notches and recesses allow the stop member to clear some cross rods that otherwise would interfere with the stop member. However, this solution requires more steps to be performed by the installer for mounting a shelf and cannot be applied if some cross rods are thicker than others.